1. Field of the Invention
The invention relates generally to apparatus for detection of the proper function of an electric fence and/or a fence charger intended to maintain charge on the fence. More particularly, the invention relates to a compact and durable sensing device which can be readily mounted onto or near an electric fence for detecting proper operation of the fence and of a charging device intended to maintain a nominally steady or periodically applied charge on the fence.
2. Description of the Prior Art
The imposition of an electrical charge on fencing intended to maintain livestock within a specified area has become well known as an alternative or addition to the fencing of livestock or the like by means of conventional fencing intended to retain such stock by virtue of the strength of the fencing rather than by an electrical charge which causes the stock to avoid the fencing. Electric fencing is charged to an appropriate voltage by means of fence charging apparatus which typically apply either continuous or pulsed current to at least one electrical conductor comprising the fencing. Examples of presently available electric fence chargers include the random pulse charging apparatus of Phillips et al which is disclosed in U.S. Pat. No. 4,316,232. McKissack, in U.S. Pat. No. 4,859,869, discloses the use of transformers for applying a continuous charge for energization of an electric fence. Standing, in U.S. Pat. Nos. 4,394,583 and 4,691,084, describe electrical fence chargers as does Shaw et al in U.S. Pat. No. 5,381,298.
While electric fence and fence charger combinations usually provide satisfactory operation, certain circumstances can occur whereby a fence can lose its electrical charge either by failure of the fence charger or by damage to the fence itself such as by cutting of the fence or other circumstance which causes an open circuit or xe2x80x9cshortxe2x80x9d condition. While fence charging apparatus may employ visual or audible signals on the apparatus itself to indicate failure or incipient failure of the fence charger, it is not possible to determine these conditions unless personnel are deployed in the area of the fence chargers per se in order to detect such indications. Accordingly, a need has been felt in the art to provide a simple and inexpensive means by which an observer at essentially any location along an electric fence can be informed of the operational state of the electric fence so that a determination can be made in the event of an indicated failure as to whether a failure of the fence charger exists or whether conductive elements of the electric fence have been breached such as by cutting or other separation thus causing an open or short circuit. The art has previously provided monitoring and alarm systems used in association with electric fences and fence chargers. Begg, in U.S. Pat. No. 4,523,187, provides one such alarm while Pope et al, in U.S. Pat. No. 4,220,949, provides a fence monitor as does Hamm in U.S. Pat. No. 5,550,530. McCutchan et al, in U.S. Pat. No. 4,297,633, provides remote devices on electric fence sections whereby the devices transmit signals to a central control location. Although the art has provided monitoring and alarm systems such as are represented by the United States patents cited herein, the art continues to feel the need for a compact and inexpensive device which can be placed on a conductive element of an electric fence and which provides a signal, particularly a visual signal in the form of a flashing light, in the event of the inability of a fence charger to maintain an electric charge on the fence or the lack of a charge on any portion of the fence such as can occur due to heavy vegetation loading that portion of the fence or a separation of at least one of the electrical conductors of the fence such as by cutting or any separation of electrical conductors or collapse of any portion of the fence causing an open or short circuit. The present invention provides in a compact, inexpensive and exceptionally durable apparatus circuitry for sensing the operational state of an electric fence and/or the electric fence charger intended to maintain an electric charge on the fence and in the several embodiments thereof finds compatibility with known fence chargers whether pulsed or continuous.
The invention provides a compact, inexpensive and exceptionally durable device which can be simply attached at a multiplicity of locations on or in close proximity to a conductive portion of an electric fence with contact thus being provided between the fence and circuitry internal of the device, any desired number of the present devices being usable without drawing down voltage. The device of the invention in its several embodiments includes a self-contained power source such as batteries of appropriate size and voltage, a circuit board carrying circuitry elements, a source of illumination disposed within the device and a shock-resistant xe2x80x9cplasticxe2x80x9d lens which forms at least a part of a housing within which components of the device are disposed and interrelated for appropriate function. The devices of the invention may be disposed at locations sufficiently close to electrified wire fence conductors such that electric field is sensed even though the devices of the invention do not actually contact electrically charged wire conductors.
Circuitry suitable to an appropriate operation of the invention can take a variety of forms according to the invention with that part of the circuitry causing communication with the electric fence and/or with the fence charger being a clip or other mounting arrangement which simply and readily fits over an electrical conductor of the electric fence at any location of the fence or an electric potential sensing means such as an electrically conductive element housed within the device and positioned sufficiently close to an electrical conductor of the fence, the clip, other mounting arrangement or electric potential sensing means being directly connected to circuitry internal of the device, which circuitry causes operation of the device to provide an appropriate visual signal in the event of the failure of the fence to exhibit an appropriate charge or the failure of the fence charger to appropriately charge the fence. The circuitry can also sense when voltage drops below a predetermined value and provides a signal indication of such a voltage drop. A particularly useful circuit defined according to the invention includes an integrated circuit as a part of the circuitry providing control, an output from the integrated circuit causing a transistor to oscillate, oscillation of the transistor controlling a light source carried by the device. It should be understood that the light source is preferably carried within the device in order to prevent damage to the light source. In this preferred circuit, the integrated circuit functions essentially as a timer and further provides means for adopting other functions to the circuitry as desired. For example, self-test functions or the like can be incorporated into the preferred circuitry due to the presence within the circuitry of the integrated circuit comprising the timer function. In a similar vein, auxiliary subsystems can be connected into the circuitry through the integrated circuit to provide other functions without any real modification of the original circuit.
The invention further contemplates provision of a control and/or timing function by means of the operation of discrete circuit elements including at least one resistor and at least one transistor which function to control the oscillation of a transistor and thus control of the light source. It is to be understood that the light source in the several embodiments of the invention can take several forms including low voltage DC lamps of the incandescent types as well as light emitting diodes of various description, it being desirable to utilize light emitting diodes having the capability of flashing operation.
In the several embodiments of the present circuitry, it is to be noted that the circuitry is not grounded to earth ground, be it represented by earth return wires and/or earth in the vicinity of the device""s location, and that the electrical reference is at the battery negative terminal. As can be appreciated, electrical reference could also be to the battery positive terminal or any other point in the circuit that is at a nominally fixed voltage with respect to the battery negative terminal according to well-known electrical principles. Accordingly, it is thus seen that the impedance of air between the device""s circuitry and earth ground and in at least one embodiment also to the fence conductor is used to prevent lowering of the voltage of the fence charger and also to provide one or two large series impedances in a potential divider wherein a second or third series impedance is provided at the input of the device""s circuitry.
The invention in its several embodiments will be seen to be compatible with all types of fence chargers whether pulse or continuous and will accept wide ranges of supply voltages such as from 3 to 15 volts DC. The present devices function within a wide range of temperatures and within a wide range of weather conditions. The devices of the invention further will not drop the voltage of the fence charger, a clip connecting the device to the fence or an electric potential sensing means such as an electrically conductive element housed within the device and positioned sufficiently close to an electrical conductor of the fence further connecting directly to circuitry within the device and providing input from the fence charger to such circuitry. The clip provides a means for hanging the devices of the invention on a high voltage fence wire without danger of shock. The illumination source of the several devices of the invention only flashes when a fence charger is not working properly or when the fence voltage at the location of the device is below a predetermined threshold, such as occurs when the fence has an open or short circuit.
Accordingly, it is a primary object of the invention to provide a detection apparatus in several embodiments for sensing the operational state of an electric fence and/or the electric fence charger intended to maintain an electric charge on the fence, the detection apparatus being of compact, inexpensive and durable construction and housing circuitry and an illumination source driven by the circuitry, whereby the circuitry detects charge on the electric fence at any location thereof and provides an indication of malfunction when such charge does not exist due either to fence charger failure or the presence of an open circuit or a significantly higher than normal load on at least the portion of the fence where the detection apparatus is located.
It is another object of the invention to provide compact and inexpensive detection devices capable of sensing the operational state of an electric fence including operation at a reduced voltage below a predetermined level at any location thereof as well as the appropriate function of an electric fence charger, the devices of the invention being usable at multiple locations and simply being clipped to or hung on or otherwise positioned in close proximity to electrically conductive fence elements of an electric fence at any location of the electric fence to provide an indication of the appropriate functioning of the fence and fence charger without drawing down the voltage imposed on the fence by the charger.
It is a further object of the invention to provide detection apparatus for sensing the operational state of an electric fence and/or the electric fence charger whereby an illumination source carried by the apparatus will be caused to flash in the event of a failure of the fence charger or the existence of an open circuit such as can be caused by a separated fence wire.
It is a still further object of the invention to provide an apparatus for sensing the operational state of an electric fence and/or fence charger electrically connected to the fence and intended to maintain an electrical charge on the fence, the apparatus including a housing, a power supply and an indicator, the improvement comprising a first circuit carried by the housing for sensing the electric field of at least a portion of the electric fence, the circuit being ungrounded to earth, a second circuit operable by the first circuit on reduction of the electric field for operating the power supply to drive the indicator and thereby to indicate a malfunction of the fence and/or the fence charger, and means electrically connected to the first circuit for disposition relative to the portion of the electric fence to allow the first circuit to sense the electric field of said portion of the electric fence, said means being disposed sufficiently close to but not necessarily touching the electric fence to allow sensing of the electric field.
Yet another object of the invention is to provide apparatus for sensing the operational state of an electrical fence and/or fence charger electrically connected to the fence and intended to maintain an electrical charge on the fence, the apparatus including a housing, a power supply and an indicator, the improvement comprising a first circuit carried by the housing for sensing the electric field of at least a portion of the electric fence, the circuit being ungrounded to earth and a second circuit operable by the first circuit on reduction of the electric field for operating the power supply to drive the indicator and thereby to indicate a malfunction of the fence and/or the fence charger.
Further objects and advantages of the invention will become more readily apparent in light of the following detailed description of the preferred embodiments.